Detectives were today awaiting the findings of a 'Cracker'-style specialist, hoping he could help them to snare the brutal killer of Rebecca Hall.

The criminal profiler - called in to draw up characteristics and other vital information on the culprit - has begun working on the case of the teenage prostitute, whose naked and battered body was found in a Bradford alleyway.

Detective Chief Superintendent Max McLean, the officer leading the hunt, said he was currently keeping an open mind on the killer's background, saying it could be a man or woman.

He said the key to the case was Miss Hall's whereabouts in the days she went missing before her death.

The young mum, known as Becky, left her house on April 13, probably heading to the Thornton Road area where she worked.

Thirteen days later, her naked and badly-beaten body was discovered in an alleyway running behind a company car park in nearby Thornton Street.

Det Chief Supt McLean said: "Scientific evidence suggests that she had not been dead for more than four days."

He said Miss Hall may have been held against her will before being murdered and her body dumped at the spot.

But he said she may have already been at the scene when she was killed and her body gone unseen until the April 26. During the time she was missing, she made no contact with her baby son, family or friends. The clothes she had been wearing almost two weeks earlier were found close to the body.

"The key question which needs answering is where Rebecca was over this nine-day period," said Det Chief Supt McLean.

Already, more than a dozen forensic experts covering all scientific fields, including one from the National History Museum, have assessed the site where Miss Hall's body was found.

Officers urgently want to hear from anyone who saw Miss Hall, or thinks that she might have been held somewhere near to them, during the time she disappeared.

Her four-month-old son Jordan, who lived with her at Lydford House, off Elizabeth Street, Little Horton Green, is now being cared for by grandparents. Miss Hall is described as being 5ft 5ins tall with a slim build and dyed red hair cut in a bob.

Anyone with information should call the free hotline on 0800 318001.